1. Field of the Invention
The invention relates in general to systems and methods for acquiring and dispensing predetermined volumes of liquids and, more particularly but not exclusively, to piezoelectric devices and methods for dispensing and transferring small volumes of fluid in the form of single droplets or drops, typically ranging in volume from picoliters to nanoliters.
2. Description of the Related Art
Conventional piezoelectric dispensing devices have a tube that is typically entirely surrounded by and bonded to a piezoelectric actuator to produce droplets. Activation of the piezoelectric actuator transmits acoustic pressure into and through the liquid in the tube. The acoustic pressure propagates through the liquid and to a dispensing opening of the tube. This results in ejection of a liquid drop from the device.
Such conventional devices have several disadvantages. One is that their operation is highly dependent on the characteristics and properties of the particular liquid to be dispensed. Thus, disadvantageously, dispensing parameters such as droplet size cannot be independently controlled and various compensative measures have to be taken which can increase cost and reduce efficiency.
Moreover, to transmit pressure to the liquid in the tube to dispense a droplet a relatively force (energy) needs to be imparted by the piezoelectric actuator. This can not only raise system and operational costs, but can undesirably lead to degradation, damage and denaturing of the liquid. Also, this further limits the actuator's operational frequency since higher frequencies may also cause liquid degradation, damage or denaturing. The transmission of a relatively high pressure to the liquid can lead to the formation of bubbles in the liquid which can undesirably cause dispensing inaccuracies, among other undesired operational complications.
Another disadvantage of such conventional devices is that the piezoelectric actuator is structurally bonded to the tube. Since many applications of dispensing using such devices involve the use of multiple liquids, such as, but not limited to, the fields of genomics and proteomics, among others, these devices fail to provide an efficient and cost-effective approach to a system involving handling of multiple liquids in small quantities, for example, biological and chemical reagents.
Typically, there are two options, neither one desirable, of addressing this situation. One is to simply discard the piezoelectric-tube device and use a new one for further processing of other liquids. The piezoelectric actuator is a relatively expensive component, and discarding it after a single use disadvantageously adds to the cost—given that some of the applications can involve the handling of hundreds or thousands, if not more, different liquids.
The second option is to rinse and clean the dispensing tube after each use to prevent contamination. Firstly, this undesirably adds additional steps to the liquid handling in terms of both efficiency and cost of the overall process. Secondly, in spite of any stringent rinsing or cleaning routines the risk of cross contamination always exists.